The eight human herpes viruses share the ability to initiate a primary infection in a specific target tissue and to subsequently sequester themselves in a latent form. The viruses that compose this family are grouped into three classes on the basis of the site of where their primary infection occurs and where they are found during latency. Two members of this family Epstein Barr and Kaposi's Sarcoma have been implicated in the generation of tumors in humans. Regulation of gene expression from these large double-stranded DNA containing viruses results from a temporally ordered cascade of gene expression. This grant is concerned with regulation of gene expression in cells infected with herpes simplex virus (HSV), the prototype for the alphaherpesviridae. It is the expression of immediate early (IE) genes that is responsible for coordinate regulation of HSV gene expression. This laboratory has focused its efforts on characterizing the activities of IE gene products. In particular we have studied the gene products of the IE-O, IE-4 and IE-27 loci. These analyses have revealed novel functions for both ICPO and ICP27, and demonstrated that ICPs 4 and 27 interact. The novel feature of ICP27 that will be studied in this application is its RNA- dependent shuttling activity. We will continue our studies of these gene products using genetic and biochemical approaches to examine the effects of mutations to the sequences encoding these proteins. These studies will add to the understanding of how these viruses interact with their host and what the consequences of virus specified protein-protein and host-virus interactions are.